BEIJING/HONG KONG (Reuters) - Beijing is stepping up its oversight of exports of coronavirus test kits after several European countries complained about the accuracy of some Chinese-made tests.

Chinese exporters of coronavirus tests must now obtain a registration certificate from the National Medical Products Administration (NMPA) in order to be cleared by China’s customs, the NMPA said in a statement late on Tuesday.

Beijing had been encouraging Chinese firms to export test kits and other supplies to help battle the coronavirus pandemic, leading to a surge of companies offering kits to countries desperate to get a handle on the fast-moving and highly contagious disease.

Some Chinese test kit makers had been taking advantage of easier European Union regulations to get their products into the market before they were approved at home.

In March, Lei Chaozi, an official with the Ministry of Education, said China-made testing kits had already been supplied to 11 countries, including the UK, Italy and the Netherlands.

But the accuracy of some Chinese tests marketed overseas without Chinese approval have been questioned by European health authorities.

Spain withdrew a batch of rapid tests manufactured by Chinese diagnostics firm Shenzhen Bioeasy Biotechnology after the product was found to have low sensitivity, which means they were unable to detect infection sufficiently.

Bioeasy said in a statement last week the inaccurate readings could be because samples were not collected and processed correctly. Bioeasy said it failed to adequately communicate with clients on how to use the test.

Separately, a spokeswoman from China’s foreign ministry said last week that Slovak government officials had questioned the reliability of rapid tests purchased from China.

The preliminary conclusion from the Chinese consulate in Slovakia was that the inaccuracies were the result of medical workers using the kit incorrectly, the spokeswoman said.

The Slovak government did not immediately respond to requests for comment.

ANTIGEN TESTS

Bioeasy's rapid tests, as well as the tests questioned by Slovak officials, are antigen tests, a method that targets the virus' protein to detect infection and can deliver results more quickly than the alternative nucleic acid method.

But antigen tests require higher level of virus load and therefore could fail to diagnose people correctly when the samples only contain small amount of virus, Dr. Chen Guangjie, an immunology professor at Shanghai Jiaotong University, told Reuters.

New coronavirus test makers in China are entering the European market during a transition between two regulatory systems.

A stricter rule will come into force in 2022 that will require many infectious disease diagnostic product manufacturers to follow procedures that can take up to a year or more to get a CE mark that indicates approval to be legally sold in European countries.

Current regulations used by several Chinese companies allow manufacturers to obtain CE Mark after submitting a dossier of documents without compulsory verification by authorized third-parties.

Xi'an Tianlong Science and Technology, a Chinese firm which received the CE Mark in March and has been in the process of churning out testing reagents that can supply tests for over one million people, told Reuters it now can't meet its export orders.

Jam Chan, marketing general manager at Osmunda, a service firm that advises Chinese medical product firms on getting overseas approvals, said many recently developed tests in China haven't gone through strict clinical trials, which means the self-declared accuracy rate printed on the products is not properly validated.

"Better not exporting products than offering inaccurate products that can lead to fake results," said Chan. "The quality of products that have been through domestic review before being exported is at least guaranteed to some extent."

(This story has been refiled to remove extraneous word "spokeswoman" in paragraph 9)